This invention relates to a coupling unit, and more particularly to a unit for coupling a shaft to a surrounding hub for joint movement.
It is known to provide arrangements which couple a shaft to a hub through which the shaft extends, so that they can perform joint movements, for example joint rotation. Such arrangements have an inner ring which is placed about the shaft and an outer ring which is placed about the inner ring. The juxtaposed surfaces of the two rings define with one another annular gaps which taper in mutually opposite directions towards one another. Similarly tapering tensioning members are inserted into these gaps and drawn inwardly towards one another by bolts, so as to cause the inner and outer rings to be forced against the shaft and the hub, respectively.
Difficulties are experienced in some of these constructions when the arrangement is subsequently to be released again, i.e. when the tension members must be made to move outwardly of their associated gaps.
German patent No. 1,099,806 discloses an arrangement of the type in question where the wedge angles of the gaps and tension members are so selected that when the bolts are released and no longer draw the tension members together, the tension members generally tend to automatically move outwardly of their associated gaps. However, in the event of improper operation of the arrangement (e.g. by unskilled personnel) difficulties in the desired release may be experienced even with this construction.
Moreover, there are other constructions in which the wedge angles of the gaps and tension elements are chosen to be within the self-locking range, i.e. when the bolts are released the tension members remain in their positions. To avoid the need for special "pulling-off" devices in such cases, coupling arrangements have been proposed in German "Gebrauchsmuster" 7,208,307 and 7,217,467 which are to facilitate the removal (i.e. expulsion) of the tension members. However, for reasons which are evident to those conversant with the field, these proposals are not truly satisfactory.